At present, bronchodilation by xanthine type bronchodilators typified by theophylline is mainly practiced for the prevention and treatment of respiratory diseases represented by asthma. Besides, beta-receptor stimuli such as ephedrine hydrochloride have been only used symptomatolytically.
However, all the above drugs have great side effects and hence have offered a problem. However, there has been nothing for its but to administer these drugs because any excellent drug substitutable for these drugs has not been yet found.
On the other hand, 3-cyano-5-methylpyrrolo[3,2-e]-pyrazolo[1,5-a]pyrimidines of compounds having a pyrrolo-[3,2-e]pyrazolo[1,5-a]pyrimidine skeleton have been known to have excellent vasodilative effect and tracheobronchodilative effect (Japanese Patent Publication No. 88999/1994). However, these compounds have been difficult to separate their action on circulatory organs such as hypotensive effect and their action on tracheas (or bronchus) from each other. It has therefore been desired to develop a drug which selectively acts on tracheas (or bronchus).
It is therefore an object of the present invention to provide a medicine which scarcely exhibits side effects and has excellent prophylactic and therapeutic effects on respiratory diseases.